1. Field of the Invention
The present invention relates to a lead frame and a resin package using the lead frame. Furthermore, the present invention relates to a miniature photoelectron device on which a high output semiconductor laser is mounted, using the resin package.
2. Description of the Related Art
A photoelectron device including an optical semiconductor element is known, for example, from JP 6-203403A. This publication discloses the following photoelectron device. A lead frame including a die pad and inner leads whose end portions are arranged in the vicinity of the periphery of the die pad is produced, and then the lead frame is sealed with a resin to produce a resin package. This resin package is provided with an opening for exposing the die pad and the end portions of the inner leads. Then, an optical semiconductor element is mounted on the die pad in the opening, and the electrodes of the optical semiconductor element are connected by wiring to the corresponding end portions of the inner leads exposed in the periphery of the die pad. Finally, a transparent optical member is provided in the opening to seal the optical semiconductor element.
For use, such a photoelectron device is mounted on an optical pick-up device or the like that records and/or reproduces an optical recording medium such as an optical disk.
There is a tendency to pursue further miniaturization for optical disk devices, and therefore there is an increasing demand for a miniature photoelectron device. One approach to promote the miniaturization of the photoelectron device is to attain a finer pitch for inner leads constituting a lead frame.
In general, the pitch of arranged inner leads is restricted by the thickness thereof, and reducing the thickness of the inner leads is effective for the miniaturization of the pitch of the arranged inner leads. JP 5-326788A discloses a semiconductor device including fine pitched inner leads, produced by pressing the end portions of the inner leads of multiple pins to reduce the thickness. In this disclosure, the end portions of the inner leads of the lead frame produced by rolling are pressed so that the thickness thereof is reduced to ⅙ at the largest, and thus thinner inner leads can be obtained.
However, conventional photoelectron devices or semiconductor devices and methods for producing these devices have the following problems.
With the increasing capacity and further miniaturization of optical disk devices, high output is required for a semiconductor laser for an optical pick-up device, and miniaturization is required for a package on which the semiconductor laser is to be mounted. Heat generation increases when the output of the semiconductor laser is raised, and therefore good heat release properties are required. On the other hand, fine pitched inner leads are required for miniaturization. However, a resin package that achieves both good heat release properties and fine pitch has not been attained yet.
This is due to the following reason. When a die pad portion is thicker than a regular lead frame in order to ensure heat release properties, thin end portions of the inner leads, which are necessary for fine pitch, cannot be produced with high precision. In a photoelectron device including an optical semiconductor element, the optical characteristics are attained by providing an opening in a resin package to expose the die pad and the end portions of the fine pitched inner leads, and mounting an optical semiconductor element on the die pad in the opening. Therefore, when the thickness of the inner leads is reduced for fine pitch, the strength of the end portions of the thin inner leads exposed in the opening is degraded so that deformation or other problem is likely to occur. Even slight deformation of the end portions of the exposed inner leads may cause deterioration of the optical characteristics or peeling between the resin and the lead end portions.
Furthermore, for the photoelectron device for optical pick-up, miniaturization is desired, particularly in one direction of the package for convenience in its installation and arrangement. The conventional photoelectron devices are substantially rectangular in plan, and it is becoming difficult to attain further reduction of the size in the direction of the shorter side of the rectangle.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a lead frame including fine pitched inner leads and a die pad having a thickness necessary for good heat release properties. Furthermore, it is another object of the present invention to provide a lead frame having good adhesion with a sealing resin. Furthermore, it is another object of the present invention to provide a lead frame that has such characteristics and is produced easily and inexpensively.
Furthermore, it is an object of the present invention to provide a resin package that achieves both miniaturization and heat release properties. Furthermore, it is another object of the present invention to provide a resin package having good adhesion between the resin and the die pad and the leads. Furthermore, it is another object of the present invention to provide a resin package that has such characteristics and is produced easily and inexpensively.
Furthermore, it is an object of the present invention to provide a miniature photoelectron device having good heat release properties that can be used with high output, has high performance and is produced inexpensively.
A first lead frame of the present invention includes a die pad including a die pad main portion having a large thickness and a die pad peripheral portion having an intermediate thickness smaller than that of the die pad main portion, provided on at least one side of the die pad main portion, at least one support lead connected to the die pad, and at least two first inner leads having a small thickness smaller than that of the die pad peripheral portion, arranged such that the end portions thereof are opposed to the die pad peripheral portion.
According to the first lead frame, in the case where the end portions of the thin first inner leads are opposed to at least one side of the thick die pad main portion, the die pad peripheral portion having an intermediate thickness is formed on the side of the die pad main portion to which the first inner leads are opposed. When the region having an intermediate thickness is provided between the thick region and the thin region having significantly different thicknesses, a drastic change in the thickness can be eliminated, and the regions can be formed at one time by rolling. As a result, the thickness of the die pad necessary for heat release properties and the reduction of the thickness of the end portions of the inner leads necessary for fine pitch can be achieved at the same time. Thereafter, miniature leads can be formed easily by press stamping. Therefore, the lead frame including the fine pitched inner leads and the die pad having good heat release properties can be obtained easily and inexpensively.
A second lead frame of the present invention includes a die pad including a die pad main portion having a large thickness, at least one support lead connected to the die pad, and at least three first inner leads having a small thickness smaller than that of the die pad main portion, arranged such that the end portions thereof are opposed to at least one side of the die pad. Each first inner lead has a narrow portion having a small width and a wide portion having a width larger than that of the narrow portion. The narrow portion is positioned on the die pad side, and the wide portion is positioned on the side opposite to the die pad. A connection point between the narrow portion and the wide portion of the central first inner lead of the at least three first inner leads is positioned farther from the die pad than connection points between the narrow portions and the wide portions of first inner leads adjacent to the central first inner lead. The gap between the central first inner lead and the adjacent first inner leads is smaller in the narrow portion than in the wide portion.
According to the second lead frame, with respect to the connection points between the narrow portions and the wide portions of the first inner leads, the inner lead positioned farther from the center has a connection point nearer the die pad. For this reason, the first inner lead positioned farther from the center has the longer wide portion. Therefore, the strength of the thin first inner leads can be kept high even in the vicinity of the end portions thereof Therefore, deformation can be suppressed during processing. The strength of the exposed end portions from the sealing resin can be improved, and deformation hardly occurs. Thus, peeling from the resin after resin-sealing can be suppressed. In addition, since the lead gap is smaller in the narrow portion, fine pitched first inner leads can be achieved as well. Furthermore, the thick die pad main portion allows good heat release properties.
A third lead frame of the present invention includes a belt-shaped thick region having a large thickness and a belt-shaped thin region having a thickness smaller than that of the thick region, these regions being in parallel with each other. A die pad is formed in the thick region, and leads are formed in the thin region, and the leads extend in a direction substantially perpendicular to that of the belt-shaped region.
According to the third lead frame, a die pad is formed in a belt-shaped thick region, so that the heat release properties are good. Leads are formed in a belt-shaped thin region, so that fine pitched leads can be attained. These belt-shaped regions having different thicknesses are in parallel with each other, and therefore can be obtained easily by rolling. In addition, since the leads extend in the direction substantially perpendicular to the direction in which the belt-shaped regions are formed, the thickness of the leads in the extending direction is uniform. Therefore, fine pitched leads can be produced easily and highly precisely. In addition, the processed leads hardly are deformed. Thus, a lead frame having fine pitched inner leads and good heat release properties can be obtained easily and inexpensively.
In another aspect of the present invention, a first resin package of the present invention includes a die pad including a die pad main portion having a large thickness and a die pad peripheral portion having an intermediate thickness smaller than that of the die pad main portion, provided on at least one side of the die pad main portion, at least one support lead connected to the die pad, at least two first inner leads having a small thickness smaller than that of the die pad peripheral portion, arranged such that the end portions thereof are opposed to the die pad peripheral portion, and a resin for sealing the die pad, the support lead and the first inner leads for integration while exposing a part of an upper surface and a part of a lower surface of the die pad and upper surfaces of the end portions of the first inner leads.
The first resin package is obtained by sealing the first lead frame with a resin, and this embodiment allows a resin package with good heat release properties including fine pitched inner leads to be manufactured easily and inexpensively.
A second resin package of the present invention includes a die pad including a die pad main portion having a large thickness, at least one support lead connected to the die pad, at least three first inner lead having a small thickness smaller than that of the die pad main portion, arranged such that the end portions thereof are opposed to at least one side of the die pad, a resin for sealing the die pad, the support lead and the first inner leads for integration while exposing a part of the upper surface and a part of the lower surface of the die pad and upper surfaces of the end portions of the first inner leads. Each first inner lead has a narrow portion having a small width and a wide portion having a width larger than that of the narrow portion. The narrow portion is positioned on the die pad side, and the wide portion is positioned on the side opposite to the die pad. A connection point between the narrow portion and the wide portion of the central first inner lead of the at least three first inner leads is positioned farther from the die pad than connection points between the narrow portions and the wide portions of first inner leads adjacent to the central first inner lead. The gap between the central first inner lead and the adjacent first inner leads is smaller in the narrow portion than in the wide portion.
The second resin package is obtained by sealing the second lead frame with a resin, and reduces peeling of the fine pitched first inner leads from the resin. Furthermore, the strength of the end portions exposed from the sealing resin can be improved. The thick die pad main portion allows good heat release properties.
In yet another aspect of the present invention, a photoelectron device of the present invention includes the first or second resin package, a photoelectron element mounted on the upper surface of the die pad, and an optically transparent member for sealing the photoelectron element.
Since such a photoelectron device has fine pitched inner leads, it can be miniature, and since it has a thick die pad, the heat release properties can be good. Such a photoelectron device can be manufactured easily and inexpensively.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.